Diffuser assembly comprising diffuser vanes pivoting about the leading edge

ABSTRACT

Embodiments of a diffuser assembly incorporate a diffuser vane with a trailing edge that changes position to improve flow performance of a compressor device. In one embodiment, the trailing edge rotates about the leading edge. This configuration maintains the position of the leading edge on the diffuser vanes relative to the orientation of the working fluid.

BACKGROUND

The subject matter disclosed herein relates to compressor devices (e.g., centrifugal compressors) and, in particular, to diffusers and diffuser vanes for a compressor device.

Compressor devices (e.g., centrifugal compressors) use a diffuser assembly to convert kinetic energy of a working fluid into static pressure by slowing the velocity of the working fluid through an expanding volume region. An example of a diffuser assembly typically utilizes several diffuser vanes in circumferential arrangement about an impeller. The design (e.g., shapes and sizes) of the diffuser vanes, in combination with the preferred orientation of the leading edge and the trailing edge of the diffuser vanes with respect to the flow of the working fluid, often determine how the diffuser vanes are affixed in the diffuser assembly.

To add further improvement and flexibility to the design, some examples of a diffuser assembly incorporate variable diffuser vanes. These types of diffuser vanes move to change the orientation of the leading edge and the trailing edge. This feature helps to tune operation of the compressor device. Known designs for variable diffuser vanes rotate about an axis that resides in the lower half, i.e., closer to the leading edge than the trailing edge of the diffuser vanes.

The location for the axis of rotation permits the trailing edge to sweep through large angles and, thus, enables better tuning and optimization of compressor performance. However, although use of these variable diffuser vanes can improve performance, implementation of the conventional designs for variable diffuser vanes move (e.g., rotate) both the trailing edge and the leading edge with respect to the incoming working fluid. This feature can have a negative impact on the performance of the compressor. The change in position of the leading edge, which results from the change in angular orientation of the diffuser vane, can cause the flow of the working fluid to prematurely separate from the surface of the diffuser vane, thus reducing the effectiveness of the variable diffuser vane to tune performance of the compressor device.

BRIEF DESCRIPTION OF THE INVENTION

This disclosure presents embodiments of a diffuser assembly that incorporates diffuser vanes with a trailing edge that changes position to improve flow performance of a compressor device. The diffuser vanes, however, maintain the position of the leading edge relative to the orientation of the working fluid. When implemented, e.g., in a compressor device, these embodiments prevent pre-mature flow separation of the incoming working fluid from the surfaces of the diffuser vane. At least this feature can provide better control and optimization of compressor performance over a large flow range.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made briefly to the accompanying drawings, in which:

FIG. 1 depicts a perspective view of an exemplary diffuser vane;

FIG. 2 depicts a detail view of the leading edge of the exemplary diffuser vane of FIG. 1;

FIG. 3 depicts a top view of the exemplary diffuser vane of FIG. 1;

FIG. 4 depicts a schematic view of an exemplary diffuser assembly that incorporates a plurality of diffuser vanes, e.g., the diffuser vane of FIGS. 1 and 2;

FIG. 5 depicts a side, cross-section view of the diffuser assembly of FIG. 3; and

FIG. 6 depicts a perspective view of an exemplary compressor device that can incorporate a diffuser assembly, e.g., the diffuser assembly of FIGS. 4 and 5.

Where applicable like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated.

DETAILED DESCRIPTION OF THE INVENTION

Broadly, the discussion below focuses on improvements in diffuser and diffuser assembly design to realize better performance in compressor devices, e.g., centrifugal compressors. In one aspect, these improvements address issues that arise as a result of re-orientation in the angular position of diffuser vanes inside the diffuser assembly. As set forth below, embodiments of the proposed diffuser assembly allow the trailing edge to be positioned as desired but maintains the orientation of the leading edge on diffuser vanes relative to the direction of flow of a working fluid that flows past the diffuser vanes in the diffuser assembly.

FIG. 1 illustrates a perspective view of a diffuser vane 100. The diffuser vane 100 has a vane body 102 with a leading edge 104 and a trailing edge 106. A chord length L defines the straight-line distance between the leading edge 104 and the trailing edge 106. The vane body 102 has an aerodynamic shape (e.g., an airfoil) with a suction side surface 108 and a pressure side surface 110 identified relative to the orientation and angle of attack of the leading edge 104 relative to a flow F of a working fluid. At the leading edge 104, the vane body 102 converges to a tip 112 with a rotation axis 114.

As shown in the detail of FIG. 2, the tip 112 is round and/or has a curvilinear outer surface 116 defined by a radius R_(TIP) that extends from a center axis 118. Other examples the tip 112 exhibit a shape (e.g., a point) that maintains the aerodynamics of the diffuser body 102. However, this disclosure also contemplates configurations of the tip 112 having less than optimal aerodynamic shapes (e.g., blunt shapes) as desired.

The rotation axis 114 resides proximate the leading edge 104 and, for example, within 5% or less of the chord length L (as measured from the leading edge 104). Depending on the size and shape of the tip 112, other exemplary locations for the rotation axis 114 can be found within an area that the radius R_(TIP) defines about the center axis 118. In one example, the rotation axis 114 is coaxial with the center axis 118 of the tip 112.

As best shown in FIG. 3, the diffuser vane 100 actuates about the rotation axis 114. In one example, the diffuser vane 100 rotates to change the position of the trailing edge 106 from a first position 120 to a second position, identified by phantom lines and the numeral 122. Such a change may accommodate changes in the direction of the flow F, e.g., from a first flow F1 orientation to a second flow F2 orientation. However, despite the relatively large angular displacement of the trailing edge 106 that occurs, the leading edge 104 is secured on the rotation axis 114 to limit changes to the position of the leading edge 104, e.g., as the trailing edge 106 moves between the first position 120 and the second position 122. This feature maintains the orientation of the leading edge 104 with the second flow F2 to reduce the likelihood of flow separation, while providing adequate adjustment of the trailing edge 106 to dictate changes in the performance, e.g., of a compressor device.

FIG. 4 illustrates a schematic view of the diffuser vane 100 as part of a diffuser assembly 124. In the example of FIG. 4, the diffuser assembly 124 includes a vane array 126 that features a plurality of the diffuser vanes 100 in circumferential orientation about an impeller axis 128. The leading edge 104 of the diffuser vanes 100 reside proximate a pivot boundary 130, which is generally identified by the phantom circle having a center axis 132. In one embodiment, a plurality of pivot members 134 secure to the diffuser vanes 100. The pivot members 134 maintain the position of leading edge 104 and, in one example, impart force to the diffuser vanes 100 to rotate the trailing edge 106 to different positions, e.g., between first position 120 and second position 122 shown in FIG. 3.

The pivot boundary 130 defines the circumferential location of the leading edges 104 of the diffuser vanes 100, e.g., relative to the impeller axis 128. Construction of the diffuser assembly 124 can affix the diffuser vane 100 to limit movement of the diffuser vanes 100 to rotation about the rotation axis 114. This configuration minimizes displacement of the leading edge 104 relative to the pivot boundary 130 and relative to one another. In one example, the rotation axis 114 on the diffuser vanes 100 align with the pivot boundary 130. However, in other examples, one or more of the diffuser vanes 100 can be spaced apart from the pivot boundary 130, e.g., aligned in a different circumferential location relative to the impeller axis 128. As shown in FIG. 4, the diffuser vanes 100 can be equally spaced apart from one another. Securing the diffuser vanes 100 in position affixes the angular spacing between the leading edge 104 of adjacent diffuser vanes 100. Such construction can ensure consistent flow separation, e.g., by placing the leading edge 104 of the diffuser vanes 100 in a known location across the vane array 126.

As mentioned above, during operation of the diffuser assembly 124, the diffuser vanes 100 in the vane array 126 can rotate (or pivot) about the rotation axis 114, e.g., to change the angular position of the trailing edge 106. The angular position accommodates changes in the direction of the flow of the working fluid. The orientation of the leading edge 104, however, remains relatively unchanged with respect to the direction and/or orientation of the flow F of the working fluid. This feature provides a much more consistent point of impact for the working fluid on the leading edge 104 throughout the vane array 126. Thus, despite the change in position of the trailing edge 106, the position of the leading edge 104 changes very little and, in turn, the diffuser vanes 100 in the diffuser assembly 124 exhibit minimal flow separation of the working fluid from the surfaces (e.g., suction side surface 108 and the pressure side surface 110 of FIG. 1) of the diffuser vanes 100.

Examples of the pivot members 134 can use a number of devices and mechanisms to rotatably secure the leading edge 104 of the diffuser vanes 100. The pivot members 134 can be an integral extension of the diffuser vanes 100 or may be fabricated such as by welding or it may be a separately attached piece of material. Pins and bearings can insert, for example, into the diffuser vanes 100 along the rotation axis 114. These elements provide a pivot and/or pivot point about which the diffuser vanes 100 can rotate. In one example, the diffuser assembly 124 can include a plurality of support devices, with one of the support devices secured to the bottom surface of each of the diffuser vanes 100. Examples of the support devices can couple with actuators, linkages, and other mechanisms to impart movement to the diffuser vanes 100 in the vane array 126. The support devices can align with the rotation axis 114 and/or be constructively offset to allow rotation of the diffuser vanes 100 about the rotation axis 114 as set forth herein.

FIG. 5 depicts a side, cross-section view of the diffuser assembly 124 taken at line A-A of FIG. 4. The diffuser assembly 124 includes one or more wall members (e.g., a first wall member 136 and a second wall member 138). The wall members 136, 138 form a diffuser cavity 140 in which the array 126 of the diffuser vanes 100 is found. In one embodiment, the pivot members 134 couple the diffuser vanes 100 to one of the wall members 136, 138. This configuration allows the diffuser vanes 100 to rotate about the rotation axis 114 to change the position of the trailing edge 104 on the diffuser vanes 100.

FIG. 6 depicts a perspective view of an example of a compressor device 200 that can incorporate a diffuser assembly (e.g., diffuser assembly 124 of FIGS. 4 and 5). The compressor 200 has an inlet 202 and a volute 204 that forms an outlet 206. The compressor 200 also includes a drive unit 208 that rotates an impeller 210 to draw a working fluid (e.g., air) through the inlet 202. The impeller 210 compresses the working fluid. The compressed working fluid flows into the volute 204 and out of the outlet 206. Examples of the compressor 200 find use in a variety of settings and industries including automotive industries, electronics industries, aerospace industries, oil and gas industries, power generation industries, petrochemical industries, and the like.

FIG. 7 illustrates a front view of the compressor device 200 in which some of the components are removed for clarity to illustrate one exemplary implementation of a diffuser assembly. The volute 204 forms at least a portion of the diffuser cavity (e.g., diffuser cavity 140 of FIG. 5). The array 126 resides in this portion of the volute 204. In one example, the array 126 is upstream of the outlet 206 During operation of the compressor 200, rotation of the impeller 210 draws a working fluid into the inlet (e.g., inlet 202 of FIG. 6). The working fluid flows into the volute 204, through the array 126, and exits the outlet 206. As discussed above, the configuration of the array 126 in the compressor 200 allows the diffuser vanes 100 to rotate about the leading edge 104 to change the position of the trailing edge 104 relative to the direction and other characteristics of the flow. Manipulation of the diffuser vanes 100, either as a group or individually, tunes the operation of the compressor device 200 to optimize various performance characteristics (e.g., flow parameters of the working fluid at the outlet 206, energy usage, etc.).

Referring now also to FIGS. 1, 2, 3, 4, 5, and 6, in operation, the drive unit 208 turns the impeller 210 to draw the working fluid through the inlet 202. The impeller 210 pressurizes the working fluid. The pressurized working fluid passes through the diffuser assembly and, in particular, through channels between adjacent diffuser vanes 100. At a high level, the diffuser assembly slows the velocity of the working fluid. The diffuser assembly discharges into the volute 204, which delivers the working fluid, e.g., to a downstream pipe that couples with the outlet 206.

Generally the compressor device 200 undergoes extensive performance testing and tuning to optimize performance for a given application. Such tuning will modify operation, e.g., of the drive unit 208, to adjust the speed of the impeller 210, which effectively modifies flow parameters (e.g., pressure, flow rate, etc.) of the working fluid that exits the outlet 206. Performance of the compressor device 200 will also change in response to the orientation of the diffuser vanes. In one example, tuning will involve adjusting the orientation of the diffuser vanes, which can modify, among other things, the pressure of the working fluid at the outlet 206. Collectively, optimization of flow parameters will likely include incremental changes to several operating parameters of the compressor device 200 to achieve a collective combination, including orientation of the diffuser vanes, that allows the compressor device 200 to operate efficiently to achieve desired flow parameters.

Examples of the diffuser vanes 100 can be constructed of various materials and combinations, compositions, and derivations thereof. These materials include metals (e.g., steel, stainless steel, aluminum), high-strength plastics, and like composites. Material selection may depend on the type and composition of the working fluid. For example, working fluids with caustic properties may require that the diffuser vanes comprise relatively inert materials and/or materials that are chemically inactive with respect to the working fluid.

Geometry for the diffuser vanes 100 can be determined as part of the design, build, and fitting of the compressor device 200 for the application. The geometry can include airfoil shapes, e.g., the shape shown in FIG. 1) for the vane body 102, examples of which take the form of wings and blades and/or other forms that can generate lift. In one embodiment, the diffuser vanes 100 can mount, e.g., to one of the wall members, using fasteners and fastening techniques that permit rotation of the diffuser vanes about the leading edge. Screws, bolts, pins, bearings, and like components can be used to maintain the position of the leading edge, while further allowing the trailing edge to change position as contemplated herein. These fasteners can secure to the wall members of the diffuser assembly, which can comprise pieces separate from the components of the compressor device or can integrate with existing hardware found in the compressor device.

In view of the foregoing discussion, embodiments of the diffuser vane and diffuser assembly contemplated herein improve performance of compressors and related devices. For example, and as set forth above, the trailing edge of the diffuser vanes rotates about the leading edge, which effectively reduces flow separation of the working fluid from the surfaces of diffuser vanes. This feature improves performance of the compressor over a larger flow range because the leading edge remains oriented with the flow direction of the working fluid.

As used herein, an element or function recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or functions, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the claimed invention should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 

What is claimed is:
 1. A diffuser assembly for a compressor, said diffuser assembly comprising: a wall member; a pivot element coupled with the wall member; and a diffuser vane coupled with the pivot element, the diffuser vane having a leading edge, a trailing edge, and a rotation axis proximate the leading edge about which rotates the trailing edge of the diffuser vane.
 2. The diffuser assembly of claim 1, wherein the pivot element aligns with the rotation axis.
 3. The diffuser assembly of claim 1, wherein the diffuser vane has an airfoil shape that converges at the leading edge to a tip with a center axis and a curvilinear outer surface.
 4. The diffuser assembly of claim 3, wherein the curvilinear outer surface is defined by a radius from the center axis, and wherein the rotation axis is found within an area defined by the radius.
 5. The diffuser assembly of claim 3, wherein the rotation axis is coaxial with the center axis of the tip.
 6. The diffuser assembly of claim 1, wherein the rotation axis resides within 5% or less of a chord length measured from the leading edge, and wherein the chord length measures the straight-line distance between the leading edge and the trailing edge.
 7. The diffuser assembly of claim 1, wherein the rotation axis aligns with a pivot boundary that defines the circumferential location of the leading edge relative to an impeller of the compressor.
 8. The diffuser assembly of claim 7, wherein the pivot element prevents translation of the leading edge from the pivot boundary when the trailing edge rotates between a first position and a second position.
 9. The diffuser assembly of claim 7, wherein the diffuser vane is part of an array of diffuser vanes that circumscribes the impeller.
 10. A diffuser assembly for a compressor, said diffuser assembly comprising: a wall member; a diffuser vane having a leading edge secured to the wall member to permit rotation of a trailing edge about the leading edge between a first position and a second position that is angularly offset from the first position.
 11. The diffuser assembly of claim 10, wherein the diffuser vane has an airfoil shape that converges at the leading edge to a tip with a center axis and a curvilinear outer surface.
 12. The diffuser assembly of claim 11, wherein the curvilinear outer surface is defined by a radius from the center axis, and wherein the diffuser vane rotates about a rotation axis that found within an area defined by the radius.
 13. The diffuser assembly of claim 11, wherein the rotation axis is coaxial with the center axis of the tip.
 14. The diffuser assembly of claim 10, wherein the diffuser vane has a rotation axis that resides within 5% or less of a chord length measured from the leading edge, and wherein the chord length measures the straight-line distance between the leading edge and the trailing edge.
 15. The diffuser assembly of claim 10, wherein the leading edge has a center axis that aligns with a pivot boundary that defines the circumferential location of the leading edge relative to an impeller axis.
 16. A compressor, comprising: a diffuser assembly comprising a wall member and an array of diffuser vanes having a leading edge and a trailing edge, wherein the diffuser vanes secure to the wall member at the leading edge to permit rotation of the trailing edge about the leading edge between a first position and a second position that is angularly offset from the first position.
 17. The diffuser assembly of claim 16, further comprising an impeller with an impeller axis, wherein the array of diffuser vanes circumscribe the impeller, and wherein the leading edge has a center axis that aligns with a pivot boundary that defines a circumferential location of the leading edge relative to the impeller axis.
 18. The diffuser assembly of claim 16, wherein the diffuser vane has an airfoil shape that converges at the leading edge to a tip with a center axis and a curvilinear outer surface, wherein the curvilinear outer surface is defined by a radius from the center axis, and wherein the diffuser vane rotates about a rotation axis that found within an area defined by the radius.
 19. The diffuser assembly of claim 18, wherein the rotation axis is coaxial with the center axis of the tip.
 20. The diffuser assembly of claim 18, wherein the rotation axis resides within 5% or less of a chord length measured from the leading edge, wherein the chord length measures the straight-line distance between the leading edge and the trailing edge. 